C4-Selective C–H Borylation of Pyridinium Derivatives Driven by Electron Donor–Acceptor Complexes

Choi, Wonjun; Kim, Minseok; Lee, Kangjae; Park, Seongjin; Hong, Sungwoo

doi:10.1021/acs.orglett.2c03882

Cited by 19 publications

(11 citation statements)

References 42 publications

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“…Under blue-light irradiation, this protocol enabled the development of valuable sulfonyl radical-mediated transformations, including alkene hydrosulfonylation, difunctionalization, and pyridylic C–H sulfonylation . This method employed electron donor–acceptor (EDA) complex-mediated radical processes exploiting pyridinium salts and a base (or phosphine), , without necessitating the use of an external photocatalyst.…”

Section: Introductionmentioning

confidence: 99%

Unlocking the Potential of β-Fragmentation of Aminophosphoranyl Radicals for Sulfonyl Radical Reactions

Kim

Jeong

et al. 2023

J. Am. Chem. Soc.

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Exploiting β-scission in aminophosphoranyl radicals for radicalmediated transformations has been a longstanding challenge. In this study, we investigated the untapped potential of β-fragmentation in aminophosphoranyl radicals by leveraging the unique properties of the P−N bond and the substituents of P(III) reagents. Our approach carefully considers factors such as cone angle and electronic properties of phosphine and employs density functional theory (DFT) calculations to probe structural and molecular orbital influence. We successfully induced β-fragmentation through N−S bond cleavage of aminophosphoranyl radicals under visible light and mild conditions, generating a range of sulfonyl radicals derived from pyridinium salts via the photochemical activity of electron donor−acceptor (EDA) complexes. This innovative synthetic strategy exhibits broad applicability, including late-stage functionalization, and paves the way for valuable sulfonyl radicalmediated reactions, such as alkene hydrosulfonylation, difunctionalization, and pyridylic C−H sulfonylation.

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Section: Introductionmentioning

confidence: 99%

Unlocking the Potential of β-Fragmentation of Aminophosphoranyl Radicals for Sulfonyl Radical Reactions

Kim

Jeong

et al. 2023

J. Am. Chem. Soc.

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“…The use of N-aminopyridinium salts in EDA complexes has been recently expanded by the same authors in their para-selective borylation of bisacodyl 119 via N-aminopyridinium salt 143 (Scheme 34). [77] They used amine-or phosphite-borane adducts 144-145 as both the Lewis base component of the EDA complex as well as the borylating agent, in analogy with what reported by Leonori (section 2.1). In contrast to the previous example, visible light irradiation was needed for the EDA complex to undergo a SET process.…”

Section: Para-addition Of Radicalsmentioning

confidence: 99%

Late‐Stage Functionalisation of Pyridine‐Containing Bioactive Molecules: Recent Strategies and Perspectives

et al. 2023

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Late-Stage Functionalisation (LSF) is an innovative technique that has been successfully applied to the CÀ H diversification of pharmaceuticals. However, LSF of the pyridine ring in drug-like molecules is often unselective. As a result, a mixture of structurally related products is obtained, thus making the purification tedious and time-consuming. This review shines a light on recent strategies addressing the selectivity issue in the LSF of complex natural products or drugs containing the pyridine moiety. Specifically, we have reviewed the efforts reported both in academia and industries with the hope of providing a guide for the LSF of elaborated pyridines.

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“…Based on the detailed mechanistic studies, the authors proposed that the EDA-complex 27A undergoes a SET event under visible light irradiation, In 2022, Hong and coworkers demonstrated a photocatalyst-free C4-selective CÀ H borylation of pyridine using N-amidopyridinium salts 61 and Lewis base under visible light illumination (440 nm) (Scheme 28). [61] The reaction parameter implied that the employment of a polar solvent significantly decreases the reaction yields. Under the optimized reaction conditions, nucleophilic Lewis base-bound borans were found suitable coupling partners with electron-deficient N-amidopyridinium salts 61 for the formation of an EDA-complex.…”

Section: N-nitrogen Containing Quaternary Pyridinium Compoundsmentioning

confidence: 99%

Recent Advances in Electron Donor‐Acceptor (EDA)‐Complex Reactions involving Quaternary Pyridinium Derivatives

Patel

Sharma

2023

Adv Synth Catal

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Quaternary pyridinium compounds are valuable intermediates in organic synthesis, which have gained immense popularity in the synthetic community. The application of transition metal or photoredox catalysis in transforming quaternary pyridinium compounds into various CÀ C and CÀ X bonds is well established. A majority of these methods require high temperatures, expansive catalysts, and delicate conditions for successful execution. On the other hand, the use of transition metal-free and photocatalysis-free strategies in constructing CÀ C and CÀ X bonds using quaternary pyridinium derivatives has been sought-after. In this context, the electron-donor-acceptor (EDA)-complex reactions have emerged as a state-of-the-art organic synthetic methodology, which do not require any photocatalyst for their successful execution. EDA-complex photochemistry takes advantage of the electron-acceptor ability of quaternary pyridinium derivatives, which can quickly generate a radical precursor via the deaminative process. These newly generated radical intermediates are useful in several valuable transformations. We hereby, in this review, discuss an area of major progress in EDA-complex mediated reactions involving quaternary pyridinium compounds with mechanism, substrate scope, and limitations.

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C4-Selective C–H Borylation of Pyridinium Derivatives Driven by Electron Donor–Acceptor Complexes

Cited by 19 publications

References 42 publications

Unlocking the Potential of β-Fragmentation of Aminophosphoranyl Radicals for Sulfonyl Radical Reactions

Unlocking the Potential of β-Fragmentation of Aminophosphoranyl Radicals for Sulfonyl Radical Reactions

Late‐Stage Functionalisation of Pyridine‐Containing Bioactive Molecules: Recent Strategies and Perspectives

Recent Advances in Electron Donor‐Acceptor (EDA)‐Complex Reactions involving Quaternary Pyridinium Derivatives

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